Power transmission fluids



Patented Dec 19, 1950 UNITED STATES ATENT OF F l-CE POWER TRANSMISSIONFLUIDS ton Spa, England No Drawing.

Application April 22, 1947, Serial No. 743,208. In Great Britain January11, 1946 8 Claims. (Cl. 252-4 9) This invention relates to powertransmission fluid of the type comprising castor oil and a diluent suchas a glycol ether.

In patent application Serial No. 552,820, now Patent No. 2,517,044,there is described and claimed a process for the preparation of a fluidfor transmission of power which comprises treating castor oil orglyceryl tri-ricinoleate in the presence of a glycol monoether, such asdiethylene glycol monoethyl ether, with an alkali or alcoholate inexcess of that required to neutralise the free acidity of thetri-ricinoleate. In making up a fluid according to the saidspecification the alkali was dissolved in a small proportion of theglycol monoether desired in the final fluid and the amount of excessalkali was determined by previous trial, allowing the mixture to standuntil substantial neutrality was attained and then determining the watertolerance of the mixture. In this way optimum proportions could bedetermined, and when the point of substantial neutrality was reached,the remainder of the glycol ether was added. Working in this way it wasfound possible to produce a fluid containing approximately 35% oil and65% glycol monoether with a setting point of minus 60 C. to minus 70 C.

It has now been found that an essential feature of the fluid producedaccording to this prior patent was the presence of an ester ofricinoleic acid and the glycol monoether, and that comparable fluidscould bemade by mixing together glyceryl tri-ricinoleate, a glycolmonoether and the ester of ricinoleic acid obtained by esterifying aglycol monoether with ricinoleic acid.

Further investigation has shown that the ricinoleic acid ester of aglycol monoether is a good substitute for castor oil quite apart fromwhether or not castor oil forms a constituent of the mixture, andconsequently this ricinoleic acid ester will form a satisfactory fluidfor transmission of power when diluted with any of the diluents whichhave been employed for making up fluids for transmission of powerhitherto.

According to the present invention, therefore, in its broadest aspect afluid for transmission of power comprises a ricinoleic acid ester of aglycol monoether and a diluent.

As above stated any of the diluents which have been'employed in thistype of fluid may be em ployed according to the invention, but it hasbeen found advantageous to employ a glycol monoether as the diluent, andconveniently the glycol monoether may be the same glycol ether as thatemployed for forming the ricinoleic acid ester.

The monoethyl or butyl ethers of ethylene glycol or diethylene glycolhave been found to be particularly suitable, but other mono-alkyl ethersof glycol and polyglycols may be employed according to the conditionswhich the fluid is required to stand up to. Thus, where very lowtemperaturesare likely to be met with, as in the case of fluids foraircraft purposes, the lower alkyl ethers of ethylene glycol ordiethylene glycol will be chosen rather than the higher alkyl ethers andthe monoethers of the monoor di-glycols in preference to higherpolyglycols. If castor oil is employed as an ingredient of the fluid itmay be employed in the form of neutralised castor oil or in the form ofsynthetic glyceryl tri-ricinoleate.

A fluid according to the invention may be prepared by adding theesterifled glycol monoether to the standard 35-65 castor oil-Cellosolvebrake fluid (monoethyl ether of ethylene glycol is sold under theregistered trade-mark Cellosolve) but in this case the viscosity mayhave to be adjusted by adding more of the glycol monoether because theproportion of glyceryl tri-ricinoleate will be higher than in a fluidprepared according to patent application Serial No. 552,820, now PatentNo. 2,517,044, to which no claim is made herein.

It is preferred when making upfla fluid with castor oil to start withthe constituent materials, which may conveniently be ethylene glycolmonoethyl ether (Cellosolve) glyceryl tri-ricinoleate, which may or maynot contain saponified acids obtained by neutralising castor oil and thericinoleic acid ester of ethylene glycol monoethyl ether, which will bereferred to hereinafter as Cellosolve ricinoleate. The effective rangeof the fluid may be increased by employing, instead of Cellosolve, thehigher boiling point diethylene glycol monoethyl ether sold under theregistered trade-mark Carbitol as the diluent, and in this case eitherCellosolve rioinoleate may be employed as the ricinoleic acid ester orthe ester of the corresponding diglycol ether which will be referred tohereinafter as Carbitol ricinoleate.

Table I given hereinafter shows inter alia the.

efiect of reducing the proportions of castor oil in a castoroil-Cellosolve ricinoleate-Cellosolve fluid, the flow at lowtemperatures being particularly good with mixtures containing as low ascastor oil. Further investigation has shown that a comparably good lowtemperature fluid can be obtained by eliminating the castor oilentirely. Thus a fluid consisting of:

Percent Cellosolve ricinoleate Cellosolve 70 was found to have aviscosity of secs. (Redwood No. 1) at 100 F. and to have an appreciableflow at -'70 C.

The following Tables I to IV give particulars including physicalconstants of fluids prepared in accordance with the invention incomparison with the standard castor oil-Cellosolve fluid and a fluidaccording to patent application Serial No. 552,820, now Patent No.2,517,044. In these tables the fluids marked AA were prepared inaccordance with the standard procedure for preparing castor oilCellosolve brake fluids in which pharmaceutical grade castor oil andCellosolve are mixed and suiflcient caustic potash dissolved inCellosolve added to neutralise the free acidity. The fluids marked BBwere prepared in accordance with the process described in our priorapplication Serial No. 552,820, now Patent No. 2,517,044. The fluids CC,DD and EE were prepared by mixing pharmaceutical grade castor oil withthe other ingredients without neutralising the free acidity of thecastor oil and the fluid FFI by simply mixing Cellosolve ricinoleatewith Cellosolve. The fluids CC and EE would show even better lowtemperature qualities if the free acidity of the castor oil used hadbeen neutralised with caustic potash as in the case of fluid AA.

Table I shows a comparison between the standard castor oil-Cellosolvefluid and a fluid made according to patent application Serial No.552,820, now Patent No. 2,517,044, with fluids made in accordance withthe present invention with varying proportions of castor oil and nocastor oil in respect of viscosity and flow qualities at lowtemperatures the amount of diluent (Cellosolve) being constant. Table IIshows the same comparison with the amount of Cellosolve adjusted to giveconstant viscosity. Table III shows the efiect on viscosity and flowcharacteristics of substituting in fluid EEl of Table I (a) Carbitolricinoleate and Carbitol (EEZ) and (b) Carbitol only (EE3) for thecorresponding Cellosolve constituents. While the low temperature flowcharacteristics are not unduly impaired the high temperature range isextended on account of the higher boiling point of Carbitol. Table IVshows the effect of the introduction of different proportions ofCellosolve ricinoleate into castor oil-Cellosolve fluids on the rubberswelling properties and other constants of these fluids. The higherswelling action on rubber of Cellosolve ricinoleate may, of course, becompensated in known manner by the introduction of an inhibitor.

The flow tests were made in accordance with the procedure laid down inthe British Air Ministry specification D. T. D. 391 or the Director ofTechnical Development. According to this speciflcation the fluid to betested is contained in a glass U-tube having a bore 3.4 mm. to 3.6 mm.diameter, the radius of the bend being such that the distance betweenthe limbs of the U-measured from wall to wall is 10 mm. The bend of thetube must be such as to allow a steel ball of diameter within thespecified limits of the bore of the tube to pass from one end of thetube to the other.

In carrying out the test the tube is filled to a depth of 10 cm. in eachlimb and placed in a freezing mixture adapted to give the requiredtemperature, such as solid carbon dioxide and alcohol. One limb of thetube is attached to pressure apparatus through a cock which may beopened when the flow test is made to give an air pressure equal to 12"head of water. The other limb is attached to a graduated horizontalcapilliary to measure the flow of fluid in the U- tube, which isobserved by the movement of a bubble in the graduated capilliary whichis calibrated for each U-tube used. Before applying the pressure andmaking the fiow test the freezing mixture is maintained at the requiredtemperature plus or minus 0.5 C. for two hours.

Table I.C'omparison of fluids made with equal proportions of solventFlow in cms. in U-tube Composition by volume Viscosity at 40 C. at C. atC. at C Castor Oil,30% 40 seconds (1) Nofiowin (1) No flow in Fluid AAL.Cellosolve, 70% Redwood No. 60 secs. 60 secs.

KOH to neutralise l at F. Castor Oil, 30% (I) 0.75 Cm. in Fluid BB1Cellosolve, 70% 38 seconds at (I) 1 cm. How 60 secs.

" KOH reacted according to applica- 100 F. in 20 secs. (2) 0.75 cm. in

tion Serial No. 552,820. (1) n M60 secs. Castor on 207 1cm. ow l l cn lscus Fluid oo1. {CellosolveRiciimlenta 10% F P at 1009 1 3 53 gg y ggCellosolve in 1 sec. 60 secs. Castor Oil 107 1 1 cm. in 2 (l) MeniscusFluid DDl. {Cellosolve'Rici nolcatc, 20% P 582 at 0 1 :g 3 ggfg igCellosolve 70% secs. (1) 60 secs. castor 051,57 1 cm. in 3 1 1 cm. inFluid EE1 Cellosolve Ri inoleate, 25% at Secs-i Oenosolvc, 70% 1 0 1- m3 1 m. in

(l) 1 secs. 4 (I) 1 Bsecs.

cm. in cm. Fluid FF! {Cellosolve Ricinolcate, 30%. }35 secs. at 100secs. 11 sec Cellosolve, 70% F. (2) 1 cm. in 6 (2) 1 cm. in sees. 23secs.

Table II.Comparison of fluids made to equal viscosity Flow in cms. inU-tube Composition by volume Viscosity @40 C. @50 C. @60 C. @70 C 38seconds (1) No flow in 60 Fluid AA g g (1) 3 in 60 g g- 60 r" 1 0. secons. o ow 1n 5 o i 'g fjf 100 F. seconds.

1,00 1)075cm fio 38 seconds (1) 1 cm flow in in 00 secs Flmd g fgf gl gggg 100 r. seconds. 2) 0.75 cm in so N0.552,820. (1) 1 fl 11 6 l o ow in0 Castor 19% 38 seconds l se ai ow m pp.). seconds. Fluld g$ Rlcmoleaie,100 F. 2 1 cm. flow in 2 No flow in 60 1 sec. (App.). seconds. CastorOil, 12.5% Fluid nog gfgggf Rlcmfleatei as seconds 1 1 cm. flow inCellosolve, 67.0% 36 secs- Castor Oil, 6% Fluid EE CellosolveRicinoleate, 38 seconds (1) 1 cm. flow in (1) 1 cm. flow in 31%. 100 F.5 secs. 9 secs.

Cellosolve, 63%

Table III .-C'omparison of fluids made with equal proportions ofCarbz'tol as solvent Flow in ems. in U-tube g i gg by Viscosity at 40 C.at C. at C. at -70 C i 50 seconds (1) No flow in 60 Castor 011, 307Fluid Alia. {CarbitoL 70%.? is d 5 secmlds- KOH to neutralise. 6 F.Castor Oil, 5% (1) 0.25 cm. flow (1) No flow in 00 (1) No flow Fluid EF2Carbitol Ricinoleate, 42 seconds at in sec. sees. in 60 secs.

25%. 100 F. (2) 0.25 cm. flow (2) M e nis on s (2) Meniscus Carbitol,70% in 60 secs. change in 60 secs. (change in 0 secs. Castor Oil, 5% (1)1 cm. flow in 7 (1) 1 cm.ilowin 15 (1) 0.5 cm. in F1111 d E133Gellosolve Ricinoleate, 42 seconds at secs. sees. 60 secs. 25%. 100 F.(2) 1 cm. flow in 5 (2) 1cm. flow in 18 Carbitol, 70% secs. secs.

Table IV.Other earperimental data obtained on fluids of Table I RubberWater Swelling Organic Acidity pH Toler- Tests 1 ance Percent PercentFluid AAl 7. 2 0.08 Ingm. KOH/gm. 9. 41 12 Fluid BBL. 9.3 0.14 mgm.KOH/gm. 9. 63 22. 4 Fluid DD1 11.13 0.38 mgm. KOH/gm. 6. 74 10. 0 FluidEEl ll. 60 0.28 mgm. KOH/gm.. 7. 43 10. 0

! Per cent volume increases after 24 hours at 70 0.

What we claim is:

1. A fluid for transmission of power consisting of 30 volumes of thericinoleic acid ester of the monoethylether of ethylene glycol, and '70volumes of the monoethyl ether of ethylene glycol.

2. A fluid for transmission of power consisting of about 30 volumes of aricinoleic acid ester of a glycol monoether and about 70 volumes of aglycol monoether.

3. A fluid for transmission of power consisting of 30 volumes of aliquid selected from the group consisting of ricinoleates of the glycolmonoethers and mixtures of the latter with castor oil and 70 volumes ofa glycol monoether.

4. A fluid for transmission of power consisting of 30 volumes of aliquid selected from the group consisting of ricinoleates of the glycolmonoethers and mixtures of the latter with castor oil and 70 volumes ofthe monoethyl ether of ethylene glycol.

5. A fluid for transmission of power consisting of 30 volumes of aliquid selected from the group consisting of ricinoleates of the glycolmonoethers and mixtures of the latter with castor oil and 70 volumes ofthe monoethyl ether of diethylene glycol.

6. A fluid for transmission of power consisting of 30 Volumes of thericinoleic acid ester of ethylene glycol monoethyl ether and 70 volumesof the monoethyl ether of diethylene glycol.

7. A fluid for transmission of power as claimed in claim 4, wherein thericinoleate liquid selected consists of 5 to 20 volumes of castor oiland the remainder is the monoethyl ether of ethylene glycol.

8. A fluid for transmission of power as claimed in claim 5, wherein thericinoleate liquid selected 7 8 1 consists of 5 to 20 vo lumes of castoroil and the UNITED STATES PATENTS remainder is the monoethyl ether ofdiethylene Number Name Date glycol 2 102,325 Woodhouse et a1. Dec 21,1937 WILLIAM PERCIVAL SMITH- 2,205,183 Woodhouse et a1. June 18, 1940HOWARD JOHN WILKS- 5 2,232,581 Woodhouse et a1. Feb. 18, 1941 2,255,208Fife Sept. 9, 1941 REFERENCES CITED The following references are ofrecord in the file of this patent: 10

1. A FLUID FOR TRANSACTION OF POWER CONSISTING OF 30 VOLUMES OF THERICINOLEIC ACID ESTER OF THE MONOETHYLETHER OF ETHYLENE GLYCOL, AND 70VOLUMES OF THE MONOETHYL ETHER OF ETHYLENE GLYCOL.